Biomechanical analysis of tension band wiring （TBW） of transverse fractures of patella

Purpose： Tension band wiring is commonly used for fixation of simple transverse fractures. The popular configuration is parallel Kirschner wires （K-wires） and a stainless steel wire loop placed in a vertically oriented figure-of-8. Methods： We used a wooden model of a patella with a midway transverse fracture and compared four different types of fixation. The first construct had a vertical figure-of-8 with one twist of wire. The second contained a vertical figure-of-8 with two twists of wire. The third was a vertical figure-of-8 with two twists of wire placed at adjacent corners while the last one had a horizontal figure-of-8 with two twists of wire placed at adjacent corners, lnterfragmentary compression at the point of wire breakage was measured for each construct as well as permanent displacement on cyclic loading. Results： Placement of the figure-of-eight in a horizontal orientation with two wire twists at the corner improved interfragmentary compression by 63% （p 〈 0.05, Tukey post ]hoc test）. On cyclic loading, all the constructs with vertical figure-of-eight but none with a horizontal construct failed （p = 0.01; Fisher＇s exact test）. Permanent fracture displacement after cyclic loading was ,57% lower with horizontal figure- of-eight constructs （p 〈 0.05; t test）. Conclusion： Placing wire twists at the corner and a horizontal placement of figure-of-8 improves stability of the construct.

A Double Tension Band Technique for Patellar Fractures—A New Concept

Amongst the many known techniques used for the management of fractures of the patella, the tension band wire fixation is a reliable treatment modality and has given consistently good results. In transverse patellar fractures, a combination of cerclage wiring and tension band fixation gives a good mechanical stability and an environment conducive to healing. The fracture described herein is classified as 45-C1 (based on Orthopaedic Trauma Association classification) of the right knee of a forty three years old male patient. It was fixed with three vertical 1.5 mm K wires and double cerclage wire looped proximally through the quadriceps tendon and distally through the patellar ligament in a double figure-of-eight configuration. The average follow-up period was 7 months. The Activity of Daily Living Scale (ADLS) of the Knee Outcome Survey was used to assess symptoms and functional capability of the knee. The fracture union was achieved at an average of 10 weeks. Full range of knee motion was achieved by end of the third postoperative month. No complications, such as infection and implant failure were noted. The technique aims to stress the advantage of giving a balanced fixation addressing the bony elements (the fractured ends) as well as the soft tissue (the extensor apparatus).

Biodegradable magnesium pins enhanced the healing of transverse patellar fracture in rabbits

Displaced fractures of patella often require open reduction surgery and internal fixation to restore the extensor continuity and articular congruity.Fracture fixation with biodegradable magnesium(Mg)pins enhanced fracture healing.We hypothesized that fixation with Mg pins and their degradation over time would enhance healing of patellar fracture radiologically,mechanically,and histologically.Transverse patellar fracture surgery was performed on thirty-two 18-weeks old female New Zealand White Rabbits.The fracture was fixed with a pin made of stainless steel or pure Mg,and a figure-of-eight stainless steel band wire.Samples were harvested at week 8 or 12,and assessed with microCT,tensile testing,microindentation,and histology.Microarchitectural analysis showed that Mg group showed 12%higher in the ratio of bone volume to tissue volume at week 8,and 38.4%higher of bone volume at week 12.Tensile testing showed that the failure load and stiffness of Mg group were 66.9%and 104%higher than the control group at week 8,respectively.At week 12,Mg group was 60.8%higher in ultimate strength than the control group.Microindentation showed that,compared to the Control group,Mg group showed 49.9%higher Vickers hardness and 31%higher elastic modulus at week 8 and 12,respectively.At week 12,the new bone of Mg group remodelled to laminar bone,but those of the control group remained woven bone-like.Fixation of transverse patellar fracture with Mg pins and its degradation enhanced new bone formation and mechanical properties of the repaired patella compared to the Control group.